This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light and not as admissions of prior art.
In conventional drilling operations, a string of drill pipe or other drilling tubular is lowered into a wellbore. The lower end of the drill string typically includes a bottom hole assembly (BHA), which features a drill bit that can be rotated to cut into the subterranean formation to advance the wellbore through the formation. Some existing systems utilize a downhole drilling motor that is part of the BHA to rotate the drill bit.
Downhole drilling motors include a drive shaft that may be coupled to the drill bit to rotate the drill bit at a desired rate. The drive shaft is located inside a housing and designed to rotate with respect to the housing. Existing downhole drilling motors typically include a bearing assembly designed to support the rotating drive shaft within the housing while allowing rotation of the shaft. These bearing assemblies often include a series of radial bearings, thrust bearings, or other types of bearings designed to accommodate the forces expected on the rotating components of the downhole motor. In general, thrust bearing assemblies may include several thrust bearings designed to dissipate axial forces on the drive shaft as the shaft is rotated. Such forces may come from the weight placed on the drill bit from a surface of the drilling system, as well as from fluid being pumped through the drive shaft toward the drill bit.
Unfortunately, existing thrust bearing assemblies for downhole motors are relatively complex systems that are not easily adaptable for use in a variety of drilling operations. Additionally, drive shafts in existing downhole motors often are constructed with steps or shoulders around a diameter of the shaft for engaging with the bearing assembly. Such steps can lead to undesirable force concentrations in the shaft, thus lowering the lifetime of the drive shaft.